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arXiv · 1004.2245

Linear-optical processing cannot increase photon efficiency

D. W. Berry·A. I. Lvovsky
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Abstract

We answer the question whether linear-optical processing of the states produced by one or multiple imperfect single-photon sources can improve the single-photon fidelity. This processing can include arbitrary interferometers, coherent states, feedforward, and conditioning on results of detections. We show that without introducing multiphoton components, the single-photon fraction in any of the single-mode states resulting from such processing cannot be made to exceed the efficiency of the best available photon source. If multiphoton components are allowed, the single-photon fidelity cannot be increased beyond 1/2. We propose a natural general definition of the quantum-optical state efficiency, and show that it cannot increase under linear-optical processing.

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D. W. Berry, A. I. Lvovsky. 2010-04-13. Linear-optical processing cannot increase photon efficiency. https://doi.org/10.1103/physrevlett.105.203601

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